Telephone system



June 2, 1925.

A. H. DYSON TELEPHONE SYSTEM Filed March 13, 1905 4 Sheets-Sheet 1 INvENT0R:--

VWITNESSES i W 1' June 2, 1925.

A. H. DYSON TELEPHONE SYSTEM Filed March 13, 1905 4 Sheets-Sheet 2 INvENToR:

mumm WITNESSES A W June 1.925! 1,540,061

A. H. DYSON TELEPHONE SYSTEM Filed March 13, 1905 4 Sheets-Sheet 3 yum? June 1925- A. H. DYSON TELEPHONE SYSTEM Filed March 13, 19-05 lllllllll lllIllllllllllllllllllllll llllllll lIllIlllllllllllllllllllll 4 Sheets-Sheet 4 INVENTOR Patented June 2, 19 25.

UNITED STATES a 1,540,061 PATENT OFFICE.

ALFRED i1. DYSON, or cHIcAeo, ILLINOIS, A-ssrenon, BY mnsnn ASSIGNMENTS, 'ro KELLOGG swIrcIIBoARn & SUPPLY COMPANY, A CORPORATION or ILLINOIS.

TELEPHONE SYSTEM.

Application filed March 13, 1905. Serial No. 249,804.

To all whom it may concern:

Be it known that I, ALFRED H. DYSON, a citizen of the United States, and resident of Chicago, county of Cook, and State of Illinois, have invented new and useful Improvements in Telephone Systems, of which the following is a specification.

My invention relates particularly to telephone exchange systems in which the connection of subscribers lines is secured by automatic mechanlsm at the central ofiice,

actuated by means of switching mechanism at subscribers stations.

An object of my invention is to provide a system in which the number of working parts and the number of electromagnets used for operating them may be comparatively few in number. A

One means employed in the furtherance of these objects consists in a, simplification of that'portion of the apparatus individual to each of the subscribers lines, which apparatuses are, in percentage systems, more numerous than any other class. Another means involves the employment of certain individual parts of the apparatus in several different capacities; notably the private or busy test circuits are also employed for restoring purposes. These and other features of my invention will be more particularly pointed out in the description and claims.

'In the systems which I have had especially; in mind in developing my invention, there is .provided for each subscriber to an exchange a switch individual to his line. and auxiliary switches employed co-operatively with the individual switches in the estab-.

lishment of connectionslbetween subscribers. In the systems to which I refer, these individuah switches have ordinarily been of a type called selector switches and provide means whereby subscribers are enabled to select various groups of auxiliary switches, the said groups respectively being common for connection to certain groups of subscribers. This selection isdetermined by the subscriber by means of switching mechanism at his substation. After he has selected the group of switches desired, hisindividualswitch thereuponautomatically, or withoutthe'volition of the subscriber. operates to pick 01 11. the first idle switch of the'group selectediby the subscriber: It will be read- ;ily understood that a switch of this charact81',fi00tlllg switching movements under the A feature of my invention consists in replacing selector switches, as switches individual to subscribers lines, by simpler switches, which may be called private switches, of which is" required the automatic operation above referred to only. In so doing, I place the comparatively complicated selector switches in the position of auxiliary switches. 'As the number of auxiliary switches may be proportional to the number of co-existing calls which it is expected will exist in an exchange, and not proportional to the number of subscribers, it will be apparent that I am, by the arrangement above mentioned. enabled to greatly reduce the number of selector switches required for a given number of subscribers.

In accomplishing this, I may increase the total number of switches required for a given number of subscribers, but taking the, system as a whole, its complexity may be materially decreased, which is one of the objects of my invention. A'further object is to decrease the initial cost of an automatic telephone exchange switchboard of the general type referred to, and a-further object is to reduce the'cost of operating and maintaining the same.

Assuming-a proposed telephone exchange, of the character above referred to, for ten thousand subscribers with grou of auxiliary switches containing eac switches equal in number to ten per cent of the numwould be effected by the employment of my invention. For ten thousand individual first selector switches may be substituted ten thousand individual private switches of materially simpler construction. Nine thousand individual first selector switches may be dispensed with and one thousand may; be retained and employed as auxiliary switches common for connection to-all subscribers in the exchange. The ten thousand private; switches of such an exchange may be conveniently d1v1ded1nto one hundred groups of one hundred switches each, and

ten first selector switches may be associated with each of said groups in such a manner as to be common for connection from the switches of the group (and exclusively so) with which they are associated. There would also be one thousand second selector switches arranged in groups, the switches of each group being common for connection to a group of one thousand subscribers lines. Each first selector switch would be adapted-for connection to at least a portion of each group of second selector switches. There would also be one thousand connector switches arranged in groups, the switches of each group being common for connection to the lines of one hundred subscribers. Each second selector switch would be adapted for connection to at least a portion of each group of connector switches associated with 1 its respective onethousand lines. It is to be understood that the proportio of auxiliary switches of each class to the number of lines in the exchange and the number of classes of auxiliary switches maybe varied to suit varying requirements,'and the grouping of switches'may be other than that outlined, without departing from the substance of my invention. I, therefore, desire not to' be limited to the arrangements described.

Generally speaking, it may be said that the subscribers private switch acts only to prepare the substation switching mecha nism for effecting a connection by placing a first selector switch under its control; that the first selector switch under its control picks out a one-thousand-line group of sub scribers as determined by the calling "subscriber; that the second selector sw tch under its control picks out the desired onehundred-line group of the selected onethousand-line group; andthat the connector switch under its control picks out the in dividual line of the one-hundred-line group selected. I.

It is in connection with such a system as this that I have elected to illustrate a (1 describe my invention, and the syst 1 disclosed in Figure 1 may be considered as illustrating such a system.

It will be readily understood by ,those skilled in the art that my invention is not limited to the particular arrangement in connection with which-I illustrate and describe it, but may be applied to systems of varying description. It will also be understood that it is not to be limited to the particular type of private, selector and connector switches which I have shown, but that switches of any approved character may be employed.

, While I have shown in Fig. 1 a system adapted for ten thousand lines and with the subscribers private switch adapted to connect with a first selector, it is obvious that for smaller sized exchanges the first and second selector switches may be omitted and the subscribers private switch adapted to directly pick out and connect with an idle connector switch by wiring the connector switches to the bank contacts of the private switch.

Referring to the drawings, Figure 1, con sisting of Sheets 1 and 2, illustrates diagrammatically two telephone lines extending from substations to the exchange with telephone exchange switchboard apparatus and circuits arranged in accordance with my invention.

Figure 2 illustrates a type of automatic switch which may be employed in connection with the circuit arrangements shown at D, E and F of Figure 1. The arrangements at D, E and F differ one from the other, and the switch shown in Figure 2' is generic. to all of them, mechanical features and movements of the machine being referred to in the detailed description of Figure 1, for the purpose of illustrating in concrete mechanical forms, work done by the said arrangements.

Figure 2*, Figure 2", Figure 2, Figure 2 and Figure 2 illustrate details of the switching mechanism shown in Figure 2.

Figure 3 illustrates a type of automatic switch which may be employed in connection with the circuit arrangements shown at C and G in Figure 1.

The mechanical operation of the switch shown in Figure 3 is as follows: A current of comparatively small volume is first caused to pass through the winding of relay 22. This causes the attraction. of its light armature 21 which closes contact between springs 27 and 26 and also between springs 25 and 24. This first flow of current does not energize. the said relay sufficiently to cause the attraction of heavy armature 23. The closure of contact between springs 26 and 27 establishes a local circuit for the flow of current through the winding of magnet 15, energizing said mag net. Contact pieces 301, 302, 303, 304, etc.. to 320 are of the following characters. Contact pieces 301, 303, 305, etc., designatedby the odd numbers, represent terminals of ten first selector switches. Contact pieces 302, 304, etc., those designated by even numbers, have permanent local ground connections. Wiper 44 is arranged to engage at all times with one or the other of its three arms illustrated, one of the contact pieces above described. It normally rests in engagement with a contact piece, the terminal of one of the selector switches which may or may not be a busy switch. The energizes tion of magnet 15, above referred to, attracting armature 16, causes a forward movement of pawl 16 attached to the said armature, causing a rotary movement of circular ratchet 44 to which wiper 44 is rigidly attached. This effects a correspond ing rotary movement of the said wiper, moving it out of engagement of a contact piece, the terminal of a selector switch, and into I engagement with a contact piece having a gagement. with an adjacent ratchet tooth.

Circuits are provided, described hereinafter in connection with Figure 1 .whereby as long as relay 22 .is energized, magnet 15 will alternately be energized and de-ener gized, its armature breaking its circuit after each energiz'ation' but not until the said armature has been almost fully attracted, and thereupon again closing the circuit of said magnet but not until said armature is almost fully retracted, thus securing with each energization a full stroke of pawl 16". One way in which this may be accomplished is indicated in Fig. 3 in which the armature 16 of magnet 1.5 is made up of two substantially parallel parts linked by the arm 16 having lost motion with respect to the two sections. Each energization and de-energization of magnet 15 causes a rotary movement of ratchet 44 and wiper 44,

one or the other of the arms of the said wiper engaging successive contact pieces until one is reached which is insulated from ground. This will occur as soon as the wiper reaches a contact, the terminal of an idle selector switch, terminals of'busy selector switches being characterized by a connection to ground. As soon as such idle terminal is reached by one of said arms, relay 22 is de-epergized, its armature 23 is retracted by spring 23, and. circular ratchet 23 1 is moved one step from left to right by means of pawl 23. Ratchet 32, being rigidly attached to ratchet 23, moves a corresponding distance with a rotary motion from left to right, in such a manner that portion 32 of lever 32 to engage the next I tooth of ratchet 32, thereby allowing arm '32 to disengage contact point 34 and to again engage contact point 33. 1

Referring to ratchet 44, it will be understood that a plurality of wipers may be mounted upon the said ratchet and that a plurality of rows of contact pieces may be provided for such wipers respectively, and

that 'each movement of ratchet 44' may thereby be made effective to accomplish a pluralityof simultaneous circuit changes.

It will also be understood that lever. 32 may be adapted to effect corresponding movements of a plurality of circuit-changing arms similar to arm 32, and each movement of the lever may be employed to effect a plurality of simultaneous circuit changes. Referring now to Figure 2, I show a shaft 257, the upper portion of which is provided with horizontal ratchet teeth, be low which are provided vertical ratchet teeth. The said shaft is adapted to be moved vertically and with a rotary motion with respect to the banks of contactpoints' 284 and 285. Upon the shaft are rigidly mounted the pair of wipers 258 and wiper 259 which, when the shaft is raised and turned, are adapted to be placed in contact with contacts shown in banks 284 and 285 respectively.

Referring to-Figure 2, the structure of the rows of contacts may be readily understood. p

The mechanical operation of the switchis as follows: When magnet 271 is energized, its armature 272 is attracted and pawl 290, being mounted upon said armature, engages a tooth of the horizontal ratchet and raises the shaft one step up. Armature 272 is provided with arm 291 which, upon the first energization of magnet 271, raises arm 264, thereby disengaging, it from the pin shown in the illustration upon dog 292 which latter thereupon moves toward the shaft and engages with its upper portion a tooth of the horizontal ratchet, maintaining shaft 257 in whatever position it may have been raised vertically by pawl 290. Armature 272 is also provided with arm 273 which, upon the first f attraction of the said armature, lifts arm 265 out of engagement with ,the pin thereby releasing pawl 266 and rendering the said pawl movable when magnet 276 is shown upon armature 282 of magnet 281,

ratchet it is adapted to engage, a number of steps corresponding to the energizing impulses imparted to the magnet, dog 292 maintaining the shaft in its raised position after each step.

Magnet 278 is adapted, by means of pawl 279 mounted upon armature 297,to effect a rotary movement of shaft 257 by causing the engagement of said pawl upon the energization of said magnet, with the vertical ratchet teeth of the shaft,-moving wipers 258 and 259 with a rotary movement from left to Successive energizing impulses sent' right. through the magnet 27 8 effect, by means of the said pawl 279, successive rotary movements ofthe shaft. The lower portion of dog 292' is adapted to engage, when the dog is disengaged as above described the vertical rato et teeth on the shaft and maintains the shaft in whatever rotated position it may be placed by successive energizations of magnet 278. v Referring now to magnet 276: upon its armature 277 is mounted a ratchet consisting of teeth 273,274 and 275. -VVhen armature 277 is attracted by'the energization of the magnet, the ratchet mounted thereon is drawn downward with respect to pawl 266, and upon the releaseof the armature the said pawl moves out of contactwith tooth 273 and forward into contact with tooth 274. The said pawl being pivoted, and rigidly attached toarm 267, the said arm is thereby moved out of contact with contact point 268 upon which it normally rests, and into contact with contact point 269, and a second attraction and release of armature 277 again causes the forward movement of pawl 266,

moving arm 267 into engagement with contact point 270. It will be noted that in case magnet276 isin an unenergized condition, each successive energization of magnet 278 will cause a forward movement of awl 266 by means of arm 280 mounted on t e armature of magnet 278 and engaging armature 277 of magnet 276. Tooth 275 prevents further forward'movement of pawl 266 when said pawl engages said tooth.

There being ten horizontal ratchet .teeth adapted to be used l-for securing vertical movements of the shaft, and ten verticalv ratchet teeth adapted to be used for securing rotary movements of the shaft, the pair of lowing manner: The energization of the said magnet attracts its armature 282 which moves forward arm 264 pivoted upon said armature in such a manner that it engages the pin upon dog 292; at the same time, the

pin upon said armature 282 engages the ofl"- set on arm 265. Upon the de-energization of magnet 281, its armature is moved away from the core of the magnet by. spring 283 which operates to draw dog 292 out of contact with the ratchets of the shaft and retains it in its withdrawn position. same time, arm 265 is drawn backward and, being pivoted to pawl 266, returns the said pawl to its normal position, as shown in the At theillustration. The withdrawal of dog 292 outof engagement with the ratchets upon shaft 257 allows the free movement of the shaft, and the torsion of spring'262 turns the shaft with a rotary motion opposite to that effected by pawl 279. When this motion has placed wipers 25.8 and 259 out of en agement with th last contacts to the let of banks 284 and 285, shaft 257 is moved downward b gravity and rests in its normal position s own in the illustration.

Referring to Figure 2, I show a plurality of'arms associated with pawl 266 of which arm 267 is adapted to engage contact points 268, 269 and 27.0, the other arms being adapted to engage the other series of contact oints mounted in association with those esignated, respectively. This figure discloses means by which pawl 266 upon its movement may be adapted to effect a plurality of simultaneous circuit changes. It is evident that the number of circuit changes so effected may be varied as required.

Referring. to Figure 1, the operation of i the system is as follows: Assuming that subscriber A desires to be connected with subscriber B, whose number is assumed to'be 5435, the said subscriber A removes receiver 8 from hook switch 9, thereby allowing the switch hook toengage the upper one of the two anvils associated with it. This establishes a path for the flow of current as follows: from ground at private switch C,

through contact between springs 19 and20, through contact 4241, through limb of the telephone line, through the substatlon, returning over limb P of the telephone line, through contact 38-39 and through the winding of relay 22 to battery .18. This flow of current may be, due to the resistance of the telephone line, only sufiicient to ene1 gize the said relay to a degree enabling it to attract its. light armature 21, heavy armature 23' remaining in its normal position shown. The attraction of armature 21- closed'contact between springs 24 and 25 and also betweensprings 27 and 26. The closure of contact between springs '27 and 26 established a path for the flow' of current as follows: from battery 18, through the winding of magnet 15, through contact 16-17, contact 27-26, contact 3029 to ground, causing'the energization of magnet 15 and the attraction of its armature 16 out,of engagement with anvil 17 thereby opening the cir- 7 cuit of the said magnet, but not until its armature was almost fully retracted. Wipers 44, 46 and 48 normally rest in engagement with terminals of a selector switch. The

energization described of magnet 15. the 7 said magnet corresponding to the similarly designated magnet in Figure 3, ,caused wipers 44, 46 and 48 to rotate one'step, thus bringing wiper 44 into engagement witha permanently grounded COI1t8.(3t piece as described in connection with Figure 3. This established a path for the flow of current as follows: from the permanent local ground connection to the said contact piece, through wiper 44, through contact 32-33, through contact 2524, through the winding of relay 22 and to battery 18. This flow of current is overa local circuit and is of a volume sufliciently great to cause the energization of relay 22 to a degree suflicient to attract heavy armature 23. This attraction opens contact between springs 19 and 20, thereby eliminating the preexisting flow of current over the telephone line through the windingof relay 22. It also (referrmg to Figure 3) causes the pawl 23 to advance a step upon ratchet 23", engagin the tooth of the said ratchet adjacent to t at upon which it rested prior to the energization of relay 22 described. I

Referring to Figure 1, it is apparent that magnet 15 will continue to be alternatelyenergized and de-energized, each energization and de-energization causing successive rotary step-by-step movements of wi ers 44, 46 and 48 until contact between sprlngs 27 and 26 is broken. The second of suchene'rgizations causes wiper 44 to engage a contact iece, the terminal of a first selector switc The contact pieces, terminals of first selector switches associated with private switch C of subscriber A, are multipled to private switches other than that of subscriber A, and any of the said first selector switches maybe employed by any private switch to which their terminals are multipled, for making a call. In case'the first selector switch, into engagement with a terminal of which wiper 44 was placed by the above described second energization of magnet 15, is at the time of such engagement employed by another subscriber, the terminal engaged by wiper 44 will have a local ground connection through the relay 28 of a private switch individual to the line of a subscriber other than A. In this case, the flow ofcurrent over the local circuit is continued I tact pieces, terminals 0 through the winding oi relay 22 from ground, through the winding of relay 28 of the private switch of the other subscriber, through contact 34-32 of the said private switch, through wiper 44 of the said switch, to a terminal of the selector switch, through the multiple of said terminal then en aged by wiper 44 of the private switch 0 subscriber A, through contact 32-33 of the private switch of subscriber A, through contact 2524 and through thetwinding of relay 22 to battery 18, thus maintaining heavy armature 23 of the said relay in its attracted position. Magnet 15 continues to-vibrate, wiper 44 engaging alternately contact pieces permanently connected to ound and conbusy selector switches, until said wiper 44 engages the terminalot a selector switch not at that time employed in a connection. Assuming this to occur when contact piece 45 is reached, there being no ground connection at that time to the said contact piece, the local 23 of relay 22 caused arm 32 to disengage contact point 33 and to engage contact point 34 by (referring to Figure 3). the retraction of. pawl 23* causing ratchet 23 to rotate one step from leftto rlght. Arms .35, 38 and 41,

by means not shown in Figure 3, were by the aforesaid movement of ratchet 23 moved out of engagement with contact points 36, 39 and 42 respectively, and into engagement with contact points 37, 40 and 43 respectively. The engagement of arm 32 with contact point 34 placed ground upon contact piece 45 of the first selector switch and its multiples, rendering the said switch busy with respect to all other private switches having access to it. The engagement of arm 35 with'contact point 37 established a ground connection to contact point 205, rendering the line of subscriber A busy with respect to subscribers who may desire connection with his line, The engagement of arms 38 and 41 with contact points 40 and 43 opened up the circuit of relay 22 to limbs P and S of the telephone line and extended the circuits of the said limbs tov wipers 46 and 48 respectively.

Subscriber A now sends, by means of key 4, five impulses of current over the following path: from ground, through cont-act 6- 4, over li1nb P of the line, through contact 38 -40, through contact 46-47", through contact 8081, through the winding ofrelay 51 and to battery 50, causing five energizations and de-energizations of the said rea each of which causes an impulse of current to flow over the following path: from ground 56, through contact between springs 55 and 54, through contact 61-60, through magnet 62 and to battery 63.

Referring now to Figure 2 and regarding it as illustrating first selector switch magnet 62 in Figure 1 corresponding to magnet 271 in Figure 2, the five impulses of current referred to caused five successive energizations and de-energizations of magnet 271 "and caused the shaft of the first selector switch to be raised five steps upward in such a manner that wipers 258 and 259 are placed in positions horizontal with the fifth rows offcontactpieces inbanks 284 and 285 respectively, .designated a and 0 These rows of contact pieces are assumed to be terminals of second selector. switches common for connection to subscribers to whom are assigned numbers from 5000' to 5999.

Subscriber A now sends, by means of key 1, one impulse of current over the following path: from gr ound, through contact 31, over limb S of the telephone line, through contact 4143, contact 48-49, contact 8485,' through the winding of relay 52 to battery 50, causing the said relay to become energized and then de-energized. This causes an impulse of current to flow over the following path: from ground 56, through contact between springs 55 and 58, through the winding of relay 59 to battery 63, causing the energization and de-energization of the said relay. Relay 59 corresponding to relay 276 in Figure 2, pawl 266 is moved out of engagement with ratchet tooth 273 and into engagement with ratchet tooth 274. This (referring to Figure 1) accompli-shes the following circuit changes:

arms 72, 7 6, 80 and 84 disengage, respectively, contact points 73, 7 7 81 and85, and move into engagement, res ctively, with cont-act points 74, 78, 82 an 86. The enga ement of arm 72 with contact point 74 esta lished a flow of current from ground, through contact 7274, through the winding of magnet 64, through contact 6566 to battery 67, causing the energization of magnet 64. Magnet 64 corresponding to magnet 278 in Figure 2, this energization caused shaft'257 in Figure 2' to be rotated one step, and placed wipers 258 and 259 in en agement with the first contact ieces at thefieft of rows 0 and c respective y. The contact pieces in rows 0 and 0 are multipled to other first selector switches, all of which have access to the second selector switches whose terminals apswitch, the contact contact piece 89 in Figure 1 will be groundpear in the said rows. In case the first contacts mentioned are terminals of a. switch already selected by some other first selector piece corresponding to ed, and a flow of current will result over the following path: from ground, through wiper 88, through relay 69, through contact 7 6-7 8,

. through the winding of relay '59 to battery 63, causin the said relay to be energized.

The windings of relays 69 and 59 are so proportioned that this flow of current does not causet he attraction of armature 70.

The energization described of magnet 64- contact 65-66 and causing its de-energiz'ation. 0 The said magnet alternately becomes energized and de-energized as long iasarm 72 rests 1n engagement with contact point '74,. each energization and de-energization causing the wipers of the switch to engage of successive second switches. As soon as an 1dle second selector selector switch is reached assumed to be switch E,

its terminal corresponding to contact piece 89 wi ll be free from groundconnection, and the circuit above described as energizing relay 59 will be broken, causing the de-energization of the said relay 59. This effects the following circuit changes arms 72, 76, and 84 disengage respectively contact of rows 0 andlc are terminals of an idle switch, the engagement of arms 72, 76, 80 and 84 with contact points 75, 79, 83 and 87 is accomplished by arm 280 (Figure 2), relay 276 of said figure corresponding to relay 59 of Figure 1 remaining unenergized.

Subscriber A now sends, b means of key 4, four impulses of current rom ground at the substation, through contact 9091, contact 124125, through the winding of relay of second selector switch E to battery 94, causing four energizations and deenergizations of the said relay, resulting in four energizati'ons and de-energizations of magnet 106. This magnet corresponding to magnet 271 in Figure 2, regarding the said figure now as illustrating second selector switch E, the shaft of the said switch is raised upward four steps, lac ing wipers 258 and 259. in positions 011- zontal with the fourth rows of contacts in banks 284 and 285, countin from below, designated d and d respective y (Figure 2).

These rows of contacts are assumedto be terminals of ten connector switches common for connection to lines of subscribers to whom are allotted numbers running from 5400 to 5499. The said terminals are multipled to second selector switches other than E, all of which thereby have access to the said connector switches.

Subscriber A now sends, by'means of key 1, one impulse of current over limb S of the telephone line, through contact 92-93, contact 128-429, through the winding of relay 96 to battery 94. causing the energization of the said relay. This causes an impulse of current from ground 102 through the winding of relay 103 to battery 107,

energizing and de-energizing the said relay.

"energization. Arms 116, 120, 124 and 128 7 disengage respectnely contact points 111,

with terminals through contacts 46-47, 90-91, 1'35-,136,'

121, 125 and 129, and engage respectively contact points 118, 122, 126. and 130. The engagement of arm 116 with contact point 118 causes the energization and de-energization of magnet 108; and the said magnet corresponding to magnet 278 in Figure 2, wipers 132, 135 and 137 are thereby placed in engagement with the first contacts at the left of rows d and d. In case the connector switch, whose terminals the said contacts are, is not already in use by connection being made with it by another second selector switch employing it in a connection, its contact piece correspondingto contact piece 133 in Figure 1 will be insulated from ground,

and the impact of arm 280 upon armature 277 of relay 276 in Figure 2, and its withdrawal upon the de-energization of magnet 278, will cause arms 116, 120, 124 and 128 (Figure 1) to move into engagement with contact points 119, 123, 127 and 131.

In case the connector switch, whose terminals the contact pieces at the left of rows (Z and (Z are, is already employed by another second selector switch, the contact piece corresponding to contact piece 133 in Figure 1 will be grounded, and a path for the flow of current will be established from ground through the winding of relay 113, through contact 120'122, through winding of relay 103 and to battery 107 energizing relay 103. The windings of relays 113 and 103 are so proportioned that this flow of current does not cause relay 113 to. attract its armature. Magnet 108 will alternately become energized and de-energized, moving wipers 132,135 and 137 into engagement of successive connector switches. As soon as terminals of an idle connector switch are reached, the circuit through relay 103- is broken, causing arms 116, 120, 124 and 128 to engage respectively contact points 119, 123, 127 and-131. The

. engagement of arm 116 with contact point 119 opens the circuit of magnet 108, causing wipers 132, 135 and 137 to rest in engagement with the contact pieces, the terminals of the idle connectonswitch assumed to be terminals 133, 136 and 138 of connector switch F. The engagement of arm 120 with contact point 123 connects contact piece 133 and its multiples to ground, rendering the connector switch busy with respect to other second selector switches havingaccess to it.

Subscriber A now sends, by means of key 4, three impulses of current from ground,

161163, through the winding of relay 140 and to battery 139, causing three energizetions and de-energizations of relay 140. Three impulses 1 of current are thereby caused to flow from ground, through contact 14514 4, through contact 150151,

through contact 1851 86, through the 1, one impulse of current over limb S of the line through contact 4849, contact 9293,

contact 137-138, through the winding of relay 141, through contact 166-165 to battery 155, causing the energization and deenergization of the saidrelay- Thiscauses an impulse of current to flow over the following path: from ground, through contact between springs 145 and 146, through the winding of relay 147 to battery 152, causing the energization and de-energizat'ion of the said relay. Relay 147 corresponding to relay 276 in Figure 2, the following circuit changes are accomplished by its .energization and de-energization: arms 185, 189, 193 and 197 disengage respectively contact points 186, 190, 194 and 198, and engage respectively contact points 187, 191, 195 and 199.

Subscriber A. now sends, by means of key 4, five impulses of current over the previously traced path, through the winding of relay 140. Arm 185 at this time resting in engagement with contact point 187 five impulses of current are thereby caused to flow through the winding of magnet 183, energizing and (ls-energizing the said magnet five times. Magnet 183 corresponding to magnet 278 in- Figure 2, wipers 258 and 259 are moved with a rotary motion five steps from left to right until they engage the fifth pairs of contacts from the left of the third rows respectively of banks 284 and'285. These are.the terminals oflthe line of subscriber 5435., or subscriber B. This is assumed to occur when wipers 204, 206 and 208 (Figure 1) engage respectively contact pieces 205, 207 and 209. e

Subscriber A now sends, by means of key 1, one impulse of current over the previously traced path, through the winding of relay 141 to battery 155, energizing and'de-ener-- gizing the said relay. Relay 147 is thereby energized and de-energized in amanner previously described. In case the line of subscriber B is already in use, contact piece 205 is connected toground and the energization of relay- 147, attracting armature 148 into engage1'nent with anvil 149, establishes a path for the flow of current as follows: from ground through contact 205- 204, through contact 189-191, through contact 149-148, through the winding of magnet 153 to battery 154. The said magnet 153 corresponding to magnet 281 in Figure 2, the mechanism of the connector switch, upon the (ls-energization of magnet 153 when the tie-energization of relay 147 interrupts the above described flow of current, is caused to return to normal. Subscriber A now depresses key 4, which act, under the above described circumstances, causes an impulse of current to flow over a previously traced path, through the winding of relay 140, energizing the said relay. The connector switch F having returned to normal, arm 185 now rests in engagement with contact point 186. The flow of current above described energizing relay 140, caused a flow of current from ground, through contact between springs 145 and 144, through contact 150-151, through contact 185-186, through the winding of A magnet 182 to battery 184, again causing an upward movement of the shaft of the connector switch. Spring 203 is thereby caused to engage anvil 202, cutting busy back machine 210 into circuit with the line of subscriber A and causing him to receive, by means. of his receiver, the characteristic busy signal. Upon receiving the same, subscriber A causes the release of second selector switch E and first selector switch D and their returns to normal in a manner hereinafter described.

In case the line of subscriber B is not in use at the time the wipers of the connector switch engage terminals of the said line,

wiper 204 is connected to battery through contact 35-36 and no flow of current occurs, upon the energization of relay 147 in the manner described, through the winding of magnet 153, and the connector switch is not released. The energization and de-energization of relay 147 in this case causes arms 185, 189, 193 and 197 to disengage respectively contact points 187, 191, 195, and 199, and to engage respectively, contact points 188, 192, 196 and 200. The engagement of arm 189 with contact point 192 establishes a connection from ground, through contact 192-189, through wiper 204 to contact piece 205 and its multiples, rendering v the line of subscriber B busy with respect to other connector switches having access to the said line. It also caused the energization of relay 22 thereby cutting relay 22 and magnet 15 of circuit.

When subscriber A in this case' depresses key 4, causing the energization of relay 140 of the connector switch, the energization of the said relay establishes a path for the flow of current from ground, through contact 145-144, through contact 150-151,

private switch G from the talking throughcontact' 185-188, through the winding of relay 181 to battery 201, energizing the said relay and attracting its armatures 179 and 178 into engagement with anvils 175 and 176. This cuts ringing machine'174 into the metallic circuit of the-line of subscriber B and causes bell 10 of subscriber B to ring. Subscriber A then releases key 4, relay 181 is de-energized and its armatures 179 and 178 resume their normal positions, as-shown in Figure 1.

Subscriber B, in response to the call, removes receiver 8 from'switch hook 9' which allows the hook lever to engage the upper of the two anvils shown associated with it, establishing a path for the flow of current from the grounded side of battery 171, through winding 170 of relay 168, through the upper winding, as illustrated, of relay 167, through contact 180-179,through contact 193-196, through contact 206-207, over limb P of the telephone line of subscriber B, returning over limb S of the telephone line, through contact 209-208, through contact 200-197, contact 178-177, through the lower winding of relay 167, through winding 169 of relay 168 and to the active side of battery 171. Relay 168 is difli'erentially wound and the above described flow of current does notcause the energization of its core. The above described flow of current causes the energization of relay 167, its armatures 161 and 166 are attracted to engage anvils 162 and 164 respectively, establishing a path for the flow of current from the grounded side of battery 155, .throughcontact 162-161, through contact 136-135, con

tact 91-90, contact 47-46, over limb P of the telephone line of sub-scriber A, through the substation, returning over limb S of the lin through contact 48-49, contact-92-93, contact 137-138, through'the winding of relay 141, through contact 166-164 to the active side of battery 155.

Subscribers A and B are now in conversation through condensers 211 and 212,

their transmitters being energized, respectively, by currents flowing over the two tion,'subscribers A and B replace their rcceivers on the hook switches and depress keys 4 and 1 associated with their respective substations, thereby grounding simultaneously the two limbs oftheir respective telephone lines.

In case subscriber B does this first, w;inding 170 of relay 168 is short circuited upon the establishment of ground to limb P of the line at the substation, the balancing effect of the diiferential windings of the said relay is destroyed .and the core of the relay is magnetized, attracting armature 172 into engagement with anvil 173. Current thereupon flowsfrom ground, through contact 172-173, thruogh magnet 153 to battery 154, 4

- causing the energization of magnet 153. Subscriber B releases keys 4 and 1, thereby removing ground from limbs P and S of the telephone line. Receiver 8 being at this time upon the switch hook, the circuit of relay 168 is opened up at the substation, the

: I said relay is de-energized, armature 172 disgization.

"caused the de-energization of relay 167, the

armatures 161 and 166 of the said relay thereuponresuming their normal positions,

as shown in Figure 1. r i

Subscriber A, depressing keys 1 and 4 and replacing his receiver on the hook subsequent to similar action by subscriber B,

' 7 causes simultaneous energizations of relays 140 and 141, the currents energizing the said relays passing through contacts 161163 and 166165'respe cti velyL-" The similltaneans energizations ofthe said relays cause springs 142and 143 toengage, establishing a path for the flow of current as follows: from ground, through contact 123- 120 (second selector switch E), through the to the one engaged by it prio'rto the above ins Winding'of relay 113, through contact 132- 133,-contact 142- 143, through the winding of magnet 153 and to battery 154. This flow-o ing armature 114 into engagement with'an' .vil115, establishing a path for the flow of current energizes relay 113, attractcurrent' asfollows: from ground, through contact. 7 9-76 (first selector, switch D),

throughthe. winding of relay 69, through.

contact 88-89, contact 114.-,115, through .the windingof magnet 112 to battery-111,

energizing relay 69and magnet 112. The energization of relay 69 attracted armature '70 into engagement with anvil 71, establishing a path for the flow of current as fol'-,

lows: from ground, through relay 28 (pri' vate switch C) through contact 344-32, contact 44-445, contact -71, through the winding of magnet 68- and to battery 67, causing the energizationsof relay 28 and magnet .68. The energization of. relay 28 established a path for the flow of current as follows: from ground, through contact 29-31, through the winding of relay 22 to battery 18, energizing the said relay and, causing it to attract its two 'armatures whereby pawl 23 (referring to Figure 3),: associated with heavy armature 23, is caused toadvanc'e one step upon ratchet 23-", engaging a tooth of the said ratchet adjacent described energization of relay 22.

moving ground from the two limbs of the left to right.

' turn of second selector switch E to normal.

The de-energization of relay 69, due to the above described opening of its circuit, opens the circuits of magnet 68 and relay 28 at contact 71-70, thereby causing their deenergizations. The de-energization of magnet 68 (the said magnet corresponding in function. to magnet 281 in Figure 2) causes the return of first selector switch D a to normal. allows armature 29 to 'disengage anvil 31, thereby de-ener'gizing relay 22. Referring to Figure 3, the de-energization of thesaid relay allows armature 23 to be retracted by The de-energization of relay 28 spring 23"; and pawl 23, being thereby drawn backward, causes ratchet 23 tobe moved with a rotary motion one step from This movement brings portion 32"-.of lever 32 intoengagement with "a tooth upon ratchet 32?, adjacent to that engaged by the said portion before subscriber A beganthe call. Thisengagement causes a forward movement of lever 32,

and arm 32 disengages contact point .34 and engages contact point 33, thereby resuming its normal position. Referring now to" Figure 1, the above described movement of lever 32, in addition to returning arm 32 to engagement with contact point 33, also returned arms 35, 38 and 41 to their normal positions (by means not shown) in em gagement with contact points 36, '39 and 42 respectively. 7 All apparatus, used in establishing the connection between subscribers A' and B, has now been returned, to normal. It will.

be noted that wipers 44,46 and 48 of private switch 0- rest in engagement with con-.

tact pieces 45, 47 and 49 of the first selector switch used in establishing the connection; It may be said that the normal or idle position of 'a-subscribersprivate switch is one in which the wipers of the switch rest in engagement with contact pieces, the termixnals of the-first selector switch last used. 7

' In case subscriber A depresses keys 4 and 1 and replaces receiver 8 in advance of groundin ofsubscri er A causes wand1ng159 of relay cuited'; and the said relay being differentilally wound, the energizing effect of its When subscriber A releases keys 4 and 1, re-

two windings is unbalanced, its core is'mago f'limbP- of the telephone line 156 ofconnector switch F to be shortcirengagement with anvil 158-, establishing a path for the flow of current from ground, through contact 157158, through the winding of relay 140 to battery 139, energizing relay 140. Relay 141 being at this time energized, spring 142 engages spring 143,

establishing a path for the flow of current from ground, through contact 123-120 of second selector switch E, through relay 113, contact 132-133, contact l42143, through the winding of magnet 153 to battery 154, energizingmagnet 1 53 and relay 113. The

circuit conditions arising from the energization of relay 113 have been described in connection with the release operation in the case in which subscriber Bcaused the release of the connector switch, and need not be further described, the release of the second selector switch E, first connector switch D and private switch G occurring when subscriber A releases keys 4 and 1 in the manner before given. The release of keys 4 and 1 by subscriber A' in the present case causes the de-energization of magnet 153, which causes the return of the connector switch F to normal.

It will be noted that subscriber B controls only the release of the connector switch associated with his line, while subscriber A is enabled to accomplish the release of all the apparatus used by him in calling suband second selector switches.

' tional circuit of his telephone line to the line of a called subscriber, or to extend the said circuit to a switch or group of switches ,common for connection to a desired limited group of subscribers lines. When in the claims I refer to a switch without specifying selector switch or connector switch, the idea of switches of these characters is excluded. 4

' When in the claims I use the term connection to, the idea of direction is intended to be conveyed. Connection to implies to called subscribers.

Connection from conversely means from calling subscribers.

When in the claims I use the term isolate, as of a switch, I'mean that-the switch' is isolated or rendered busy with respect to other switches with which it is associated and -which have access to it.

When in the claims I use the term busy circuit, as of a switch, I mean a circuit extending fromthe said switch to another switch associated with the first, and rendering the said other switch busy with respect to other switches adapted to be placed in electrical engagement with it.

When I use the term trunk release circuit, I refer to a circuit extending between two switches in electrical engagement, in-

' cluding apparatus for causing the return of a switch to its normal position.

I claim 1. An automatic telephone system including a plurality of subscribers lines connecting substations with the central oflice, an equal plurality of automatic switches, each switch individual to one of said lines, a smaller plurality of selector switches associated with said automatic switches, each of saidselector switches being common for connection to and connection from each of said telephone lines, switching mechanism associated with the line of a calling sub-' scriber adapted to perform a preliminary switching operation for causing the automatic switch of said line to bring said line into operative relation with an idle one of.

@saidselector switches, and acentral source of current and bridges adapted to supply talking current to subscribers lines there-' from when connected.

2'. An automatic telephone system includmg a plurality of subscribers lines connect ing substations with. the central office, an

equal plurality of automatic switches, each switch individual to one of said lines, a

smaller plurality of selector switches associated with said automatic switches, each of said selector switches being common for connection to and connectlon from each of said telephone lines, switching mechanism asso ciated with the line of.a calling subscriber adapted to perform a preliminary switching operation for causing the automatic switch of said line to bring said line into operative relation with an idle oneof said selector.

switches, means for isolating said selector switch when said relation is established and a central source of current and bridges.

adapted to supply talking current therefrom to subscribers lines when connected.

3. An automatic telephone system including a plurality of subscribers lines connecting substations with the central ofiice, an equal plurality of automatic switches, each switch individual to one of said lines, a smaller plurality of selector switches associated with said automatic switches, each of said selector switches being common for connection to and connection from each of said telephone lines, switching mechanism associated with the line'of a calling subscriber adapted to perform a preliminary switching operation for causing the automatic'switch of said line to bring said line into operative a a central source of current and bridges 10 adapted to supply talking current to. sub scribers lines therefrom when connected. 4. An automatic telephone system including subscribers lines a series of groups of automatic switches at the central office, each switch individual to a subscribers line, selector switches less innumber than the total number of automatic switches, each common for connection to all subscribersin thev exhange, a grouping thereof into divisions equal in number to said groups of automatic switches, each. division being individual for connection from the lines of a single group of automatic switches and itsswitches being common for connections from the lines of the "switches of said group,

. switching mechanism associated with the.

line'of a calling subscriber adapted to perform a preliminary switching operationfor caus ng theautOmatics itch of said line to bring said line into operative relation with an idleone of said selector switches, and a central source of current and branchesadapted to supply talking current .to subtotal number of automatic switches, each common for connection. to all subscribers in theexchange, a grouping thereof into divil dividual for "connection from the lines of a sions equal in number to said groups of automatic switches, each dIVlSlOIl be ng insingle group: of automatic. switches and its swltchesbeing common for connections from the lines of the switches of said group, switching mechanism associated with the line of a calling subscriber adaptedljto perform a preliminary switching operation for causing the automatic switcliofsaid line to bring said lineinto operative relation with an" idleone of said selector switches, means-for isolating said selector switch when said relation is established, and a central source of current and bridges adapted to supply talking current to subscribers lines therefrom when connected. i v 1 6. An automatic telephone System-incIud ing subscribers lines a series of groups of automatic switches at the central ofiice, each :switch individual to a subscribers line, selector switches less in numberthan the total number of automatic switches, each common for connection to all subscribers in the exchange, a grouping thereof into divisions equal in number to said groups of automatic switches, each division being individual for connection from the lines of a single group of automatic switches and its switches being common for; connections from the lines ofthe switches of said group, switching mechanism associated with theline of a calling subscriber adapted to perform a preliminary switching operation for causing the automatic switch of saidline to bring said line into operative relation with an idle one of said selector switches, means for isolating said selector switch when said relation is established, switching devices comprised in said mechanism controlled by the subscriber' for directing switching movements of a selector switch when said relation exists in establishing a desired conversational circuit, and a central source of current and bridges adapted to supply talking current to subscribers lines therefrom when connected.

7. An automatic telephone'system including two telephone lines connected for conversartion, a central source of current asso-l ciatcd therewith, supplying current for talking purposes, a private switch and a selector switch associated with said lines at the central ofiice, contact-pieces included in said switches forming part of the talking circuit of the lines, an additional contact-piece .for each of said switches forming part of a trunk release circuit for its respective switch,

and apparatus for returning the switches to tral ofiice, contact pieces included in said switches forming part of the talking circuit of the lines, and an additional contact-piece for each of said switches forming part of a' trunk release circuit for itsrespective switch. 9. An automatic'telephone system includ-- ing two telephone lines connected for conversation, a central source of current associated therewith, supplying current for.

talking purposes, a private switch, a first selector switch, a second selector switch and; a connector switch associated with said lines, contact-pieces included in each of said switches forming part of the talking circuit, additional contact-pieces for said private switch, said first selector switch and said second selector switch one for each,-forming parts of trunk' release circuits for the-re V spective switches, and apparatus for returning each of said switches to'its normal position when conversation is finished.

10. An automatic telephone system including two telephone lines connected for conversation, a central source of current associated therewith, supplying current for talking purposes, a private switch, a first selector switch, a second selector switch and a connector switch associated with said lines, contact-pieces included in each of said switches forming part of the talking circuit, and trunk release circuits extending between said switches insulated from the talking circuit for returning to their normal positions said private switch, said first selector switch and said second selector switch.

11. An automatic telephone system including two telephone lines connected for conversation, a central source of current associated therewith supplying current for talking purposes, a private switch, a first selector switch, a second selector switch and x the exchange, switching mechanism asso ciated with the line of a calling subscriber adapted to perform a preliminary switching operation for causing the automatic switch of said line to bring said line into operative relation with an idle one of said selector switches, and a central source of current and branches adapted to supply talking current to subscribers lines therefrom when connected. 1

13. An automatic telephone system including subscribers lines, a series of groups of automatic switches at the central office, each switch individualto a subscribers line, selectorswitches less in number than the total number of automatic switches, each common for connection to all subscribers in the exchange, switching mechanism associated with the line of a calling subscriber adapted to perform a preliminary switching operation for causing the automatic switch of said line to bring said line into operative relation with an idle one of said selectoixswitches, means for isolating said selector switch when said relation is estabsubscribers lines 'therefroin when connected.

of automatic switches at the central ofiice,

each switch individual to a subscribers line, selector switches less in number than the total number of automatic switches, each common for connection to all subscribers in the exchange, switching mechanism associated with the line of a calling subscriber adapted to-perform a preliminary switching operation for causing the automatic switch of said line to bring said line into operative relation with an idle one of said selector switches, means for isolating said selector switch when said relation is established, switching devices comprised in said mechanismcontrolled by the subscriber for directing switching movements of a selector switch when said relation exists in establishing a desired conversational circuit, and a central source of current and bridges adapted to supply talking current to'subscribers lines therefrom when connected.

15. A telephone system including a telephone line, a progressive switch, line contacts for said line upon said switch, selectors having multiple contacts upon said switch, mechanism for performing a preliminary switching operation at the substation when said line is used as a calling line, to cause line contacts of said line to register with multiple contacts of an idle selector whereby said line is operatively connected with said selector, and release means for said line -effective to disconnect the same from said selector without altering the operative position of said progressiveswitch.

16. A telephone system including a telephone line, selector switches associated therewith, multiple terminals of said selector switches, an automatic'switch, means for operating mechanism of said automatic switch to cause it to connect said line with terminals of an idle selector, together with means for freeing said line from said selector when disconnection is desired without altering the selective position of said automatic switch.

17. A telephone system including a tele phone line, a selector switch, an automatic selective switch having contacts connected with said selector contlnuing said telephone line to said selector, other telephone lines, a

test circuit for said selector maintained in 4 cuit to its normal condition when disconnec tion of said line from said selector is desired without changing the selective position of said automatic switch. a

18. A telephone system including a telephone line, a selector switch associated therewith, a selective automatic switch .having contacts individual to said line, multiple matic switch, mechanism for causing concontacts of said selector switch at said autotacts ofsaid. line to register with multiple contacts of said selector, such registering being cont-rolled by the idle or busy condition of said selector, a magnet for freeing said line from saidselector when disconnection is desired, and means for operating said mag net to free said line without altering the selective position of said automatic switch as at the time of release.

19. A telephone system including a telephone line, a progressive switch, line contacts for said line upon said switch, selectors having multiple contacts upon said switch, mechanism for performing a preliminary switching operation at the substation when said line is used as a calling line, to cause line contacts of said line to register with multiple contacts of an idle selector whereby said line is operatively connected with said selector, mechanism at the substation of said line for transmitting directive currents to adjust said selector in establishing a desired connection, mechanism for restoring said selector to normal controlled from the substation, and a trunk release circuit extending to said progressive switch responsive to said mechanism efi'ective to disconnect said line from said selector without altering the operative position of said progressive switch.

20. In a telephone exchange system provided with selector switches of various classes at the exchange including connector switches adapted to cooperate with calling devices at the substations inestablishing desired connect-ions, the combination with two subscribers lines connected 'for conversation, of a selector switch of each class, contact pieces in each of said switches forming part of the conversationalcircuit, an additional contact piece included in each of said switches other than the connector switch preventing intrusion upon the conversational circuit, release circuits including said additional contact pieces, a differential relay at the exchange, and means for energizing said relay from the calling substation to operate said release circuits.

tional circuit, release circuits including said additional contact pieces, an electromagnet at the exchange having a winding through which'talking current is supplied to the calli g l e, n mean for altering the el ctricalrcondition of said winding when disconnection is desired to cause operation'of said release circuits.

22. In a telephone exchange system provided with selector switches of various classes at the exchange, including connector switches adapted to co-operate with calling devices at'the substations in establishing desired connections, the combination with a subscribers line, of a first selector switch adapted to be operated under substation control, second selector switches, multiple terminals of. said. second selector switches,

wipers included in said first selector switch adapted to engage said terminals, a part of said wipers being for conversational use, a

test wiper enabling said, first selector to select and isolate an idle second selector, means for causing a flow of current over said wiper when disconnection 1s des red,

release mechanism at the exchange operated neutralizing one another during conversation, means controlled at the calling substation for unbalancingsaid windings when disconnection is desired, and mechanism responsive to the unbalancing of said windings to cause a current flow over said contact to restore said selector. I

24. A telephone system including a calling subscribers line and a called subscribers line switched to connection at the exchange, a selector included in the connection at the exchange, a private wiper for said selector preventing intrusion, a central source of current, a difierential relay at the exchange having windings connected to opposite poles of said source, the other ends of said windings being connected together via the calling substation, a switch controlled at the calling substation for causing a preponde-rating cur rent flow in one winding of said relay when disconnection is desired, an electroma-gnet for restoring said selector, and means for energizing said magnet responsive to said preponderating flow over a circuit including said private Wiper.

25. A telephone system including a pair of connected-subscribers lines, a plurality of selective switches at the exchange connecting said lines, talking contacts included in said switches through which the conversational circuit extends, contacts included in some of said switches not forming part of the conversational circuit with means conwhich the conversational circuit extends, a

multiple private or test contact for one of said switches for preventing intrusion upon the conversational circuit, means for altering the electrical condition of said contact to restore to normal one of said switches, and a central source of operating and talking current located at the exchange.

27 A telephone system includinga telephone line, a selective switch at the exchange connected with said line, a second selectiveswitch connected with said first switch, contacts of said switches forming part of a talking circuit, an additional contact piece for said first switch in connection with a contact of said second switch serving to protect the talking circuit from intrusion, means for altering the electrical condition of said contact piece when disconnection is desired, release mechanism for restoring a selective switch responsive to said altered electrical condition, and a battery at the central exchange for supplying talking current to said talking circuit.

28. A telephone system including a telephone line, a selective switch at the exchange connected with said line, a second selective switch connected with said first switch, contacts of said switches forming part of a talk ing circuit, an additional contact piece for said first switch in connection with a contact of said second switch serving to protect the talking circuit from intrusion, a release relay, means responsive to a switch at the substation of said line foraltering the operative condition of said relay when disconnection is desired, switching mechanism controlled by said relay for affecting the electrical condition of saidcontact'piece on alteration of saidoperative condition as described, release apparatus responsive to the electrical condition of said contact piece for restoring a selective switch, and a battery at the exchange for supplying talking current tosaid talking circuit.

29. A telephone system including a telephone line, a selective switch at the exchange connected with said line, a second selective switch connectedewith said first switch, contacts of said switches forming part .of a talking circuit, an additional contact piece for said first switch in connection with a contact of said second switch serving to protect the talking circuit from intrusion, a central source of current, a relay at the exchange through which talking current from said source is supplied to the transmitter of said line, means responsive to a switch at the substation of said line for altering the operative condition of said relay when disconnection is desired, switching mechanism controlled by said relay for afl'ecting the electrical condition of said contact piece on alteration of said operative condition as described, and release apparatus responsive to the electrical condition of said contact piece for restoring a selective switch.

80. A telephone system including telephone lines, relatively movable switch contacts through which a talking circuit between calling and called lines may be completed, means, including a testing contact independent of the contacts included in the talking circuit for determining said talking circuit, means for restoring sald switch contacts to normal including a circuit through said testing contact, and a centralized source of operating and talking current.

31. A telephone system including telephone lines, relatively movable switch contacts through which a talking circuit between calling and called lines may be completed, means, including a testing contact separate from the contacts included in the talking circuit for determining the relative movement of said contacts, a circuit through said testing contact for restoring said switch contacts to normal, means for controlling said circuit, and a centralized source of operating and talking current.

32. A telephone system including telephone lines, interconnecting link-circuits and a selector switch for extending the talking circuit of a calling line to an idle link-circuit, said selector switch including a test contact for use in selecting the idle link-circuit, said test contact being separate from the contacts included in the talking circuit, means for restoring said switch to normal including a circuit extending through said testing contact, and a source of current located at the central exchange ,for supplying talking current to said calling line.

33. A telephone system including telephone lines, interconnecting link-circuits, a plurality of interconnecting automatic switch mechanisms for uniting calling and called lines by link-circuits into a talking circuit, testing contacts associated with certain of said switch mechanisms for use in determining the link-circuits to be included in said talking circuit, means for releasing one of said switch mechanisms, means in one of said switch"niechanisms for supplying talking current to said tallnng circuit, a circuit including a testing -contact, and means ope 'ated by said releasing means over said circuit to release another of said switch mechanisms.

34. A telephone system including telephone lines, interconnecting link-circuits, a plurality of selective switch mechanisms for uniting a calling and a called line by linkcircuits into a talking circuit, a testing conta associated with one of said mechanisms for selecting a link-circuit to be included in said talking circuits, a circuit for releasing one of said switch mechanisms including said testing contact, and means for controlling said circuit, said means including a relay through which talking current is sup plied to said talking circuit.

35. A telephone system including telephone lines, interconnecting linlecircuits, a plurality of selective switch mechanisms for uniting a' calling and a called line by linkcircuits into a talking circuit, a private contact separate from said talking circuit associated with one of said switch mechanisms, a connection device for contact therewith to place a busy potential upon said contact to protect the talking circuit from intrusion, a

release circuit for one of said switching mechanisms including said private contact, and apparatus for altering the potential of said private contact when disconnection is desired to render said release circuit effective, said apparatus including a 'relay through which talking current is supplied to said talking circuit.

36. A telephone system including telephone lines; interconnecting linl'r-circuits; selector and connector switches for uniting calling and called lines by certain of said link-circuits into a talking circuit, said selector and connector switches being provided with testing contacts for use in determining the talking circuit, and means for releasing said selector switch including a circuit through its testing contact in response to the release of said connector switch; and means for releasing the latter, said means including a battery serially connected through the windings of a relay to the two sides of said talking circuit.

4 37. A telephone system including a telephone line, a non-numerical non-restoring selective switch at the exchange connected with said line, a second selective switch conuected with said first switch, contacts of said switches forming part of a talking circuit, an additional contact piece for said first switch in conneition with a contact of said second switch serving to protect the talking circuit from intrusion, a release relay, means for altering the operative condition of said relay when disconnection is desired, and 'release apparatus responsive to an altered electrical condition of said contact piece produced responsive to said relay for restoring a selective switch.

38. A telephone system including tele-: phone lines, a calling telephone line, selective switching mechanisms at the exphange for use ininterconnecting lines, less in numher than the number of lines, a progressive switch at the exchange, multiple contacts of said mechanisms at said switch, contacts individual to said calling line at said progressive switch, mechanism responsive to the removal of the receiver of saidcalling line to electrically connect saidindividual contacts and multiple contacts of an idle switching mechanism, and apparatus. effective, when disconnection is desired, to operatively dissociate said line from said mechanism while maintaining said switch in its antecedent progressive position; l

39. An automatic telephone system including telephone lines, a calling'telep'hone line, selectors at the exchange for use in interconnecting lines, less in number than the number or" lines, a progressive switchat the exchange, multiple contacts of selectors at said switch, contacts individual to said calling line at said progressive switch, mechanism responsive to a preliminary impulse transmitted over said calling line to electrically connect said individual contacts and multiple contacts of an idle selector, whereby said calling line is operatively associated with said selector, means for electromagnetically adjusting said selector in establishing connection from said line to a called line, and a release circuit including a circuit controlling electromagnet for opcratively diss ciating said lineflfro-m said selector while maintaining said switch in its antecedent progressive position.

40. An automatic telephone system. including telephone lines, a calling telephone line, selectors at the exchange for use in interconnecting lines, less in number than the number of lines, a progressive switch at the exchange, multiple contacts of selectors at said switch, contacts individual to said calling line at said progressive switch, mechanism responsive to a preliminary impulse transmitted over said calling'line to electrically connect said individual contacts and multiple contacts of'an idle selector, whereby said calling line is operatively associated with said selector, a releasocircuit including a circuit controlling electromagnct for operativel; dissociating said line from said selector while maintaining said switch in its antecedenhprogressive position, a multiple contact of said selector included in said release circuit, and means for causing a cur rent flow from said selector responsive to mechanism actuated by currents over said calling line to operate said release circuit.

ll. An automatic telephone system including telephone lines, a calling telephone line, selectors at the exchange for use in interconnecting lines, less in number than the number of lines, a progressive switch at the exchange, multiple contacts of selectors at said switch, contacts individual to said calling line at said progressive switch, mechanism responsive to a preliminary impulse transmitted over said calling line to electrically connect said individual contacts to multiple contacts of an idle selector, whereby said calling line is operatively associated with said selector, a release circuit including a circuit controlling electromagnet for operatively dissociating said line from said selector while maintaining said switch in its antecedent progressive position, a multiple contact of said selector included in said release circuit, electromagnetic mechanism for causing an alteration of the electrical condition of said contact to render said circuit effective, and switching means at the substation of said line for controlling said electromagnetic mechanism.

42. An automatic telephone system including telephone lines. a calling telephone line, selectors at the exchange for use in interconnecting lines, less in number than the number of lines, a progressive switch at the exchange, multiple contacts of selectors at said switch, contacts individual to said calling line at said progressive switch, mechanism responsive toa preliminary impulse transmitted over said calling line to electrically connect said individual contacts to multiple contacts of an idle selector, whereby said calling line is operatively associated with said selector, means for eleetromagnet' ically adjusting said selector in establishing connection from said line to a called line,

a connector for subsequent operation responsive to said means, to connect directly with the calledline, and a central source of current and branches for supplying talking current to subscribers lines therefrom when connected.

4-3. An automatic telephone system including telephone lines, a calling telephone line, selectors at the exchange for use in interconnecting lines, less in number than the number of lines, a progressive switch at the exchange, multiple contacts of selectors at said switch, contacts individual to said calling line at said progressive switch, mechanism responsive to a preliminary impulse transmitted over said calling line to electrically connect said individual contacts to multiple contacts of an idle selector, whereby said calling line is operatively as sociated with said selector, mechanism effective, when disconnection is desired, to operatively dissociate said line from said selector while maintaining said switch in its antecedent progressive position, and a central source of current and branches for supplying talking current to subscribers lines therefrom when connected.

l4:- An automatic telephone system including telephone lines, a calling telephone line, selectors at the exchange for use in interconnecting lines, less in number than the number of lines, a progressive switch at the exchange, multiple contacts of selectors at said switch, contacts individual .to said calling line at said progressive switch, mechanism responsive to a preliminary impulse transmitted over said calling line to electrically connect said individual contacts to multiple contacts of an idle selector, whereby said calling line is operatively associated with said selector, means for electromagnetically adjusting said selector in establishing connection from said line to a called line, a connector for subsequent operation responsive to said means, to connect directly with the called line, a contact for said selector serving to protect the talking circuit when established against intrusion, means for altering the electrical condition of said contact for restoring purposes, an electromagnet for said selector responsive to the altered electrical condition of said contact to restore said selector, and release means for said calling line tooperatively dissociate said line from said selector while maintaining said progressive switch in its antecedent progressive position.

45. An automatic telephone system includ ing telephone lines, a calling telephone line, selectors at the exchange for use in interconnecting lines, less in number than the number of lines, a progressive switch at the exchange, multiple contacts of selectors at said switch, contacts individual to said calling line at said progressive switch, mechanism responsive to a preliminary impulse transmitted over said calling line to electrically connect said individual contacts to multiple contacts of an idle selector, whereby said calling line is operatively associated with said selector, means for electromagnetically adjusting said selector in establishing connection from said line to a called line, a connector for subsequent operation responsive to said means, to connect directly with the called line, a contact for said selector serving to protect the talking circuit when established against intrusion, a trunk release circuit at the exchange, means for altering the electrical condition of said contact to render said circuit effective when disconnection is desired, and release means for said calling line' to operatively dissociate said line from said selector while maintainingsaid switch in its antecedent progressive position.

46. An automatic telephone system including telephone lines, a calling telephone line, selectors at the exchange for use in interconnecting lines,.less in number thanthe number of lines, a progressive switch at the exchange, multiple contacts of selectors at said switch, contacts d d al t s id ca i g 

